Hi, thank you for the link to your demo website.
Well there is no script error or jQuery duplication. Everything looks as expected.
But as you already know it does not work either. The default template does not seems to make a difference:
Unfortunately I don't know how to help you.
Please try it on clean Joomla! 2.5 installation first without any other 3rd party installed extensions. Also on other server if possible (or your own local server - localhost).
Also just in case your Joomla! cache is enabled please disable it.